Figure 20.

The well-known $P-\dot{P}$ diagram on which two readily measurable quantities are plotted, period derivative against period, together with inferred magnetic dipole field strengths and spindown ages (diagonal lines). The main clump is the radio pulsars (red dots), of which around 2000 are known. At the top right are the magnetars (green triangles), and on the lower left we have old neutron stars with very weak dipole fields which have been spun up by accretion. Blue circles represent binary systems and stars supernova remnants. The so-called magnificent seven are the pink triangles on the right. Figure provided by T. M. Tauris.